Industrialist John Hammond has created Jurassic Park, a theme park of cloned dinosaurs, on the tropical island Isla Nublar, located off of the coast of Costa Rica. After a Velociraptor kills a dinosaur handler, the park's investors, represented by lawyer Donald Gennaro, demand a safety certification. Gennaro invites chaotician Ian Malcolm, and Hammond invites paleontologist Alan Grant and paleobotanist Ellie Sattler. Upon arrival, the group is shocked to see a live Brachiosaurus and other dinosaurs.
At the park's visitor center, the group learns that the cloning was accomplished by extracting dinosaur DNA from prehistoric mosquitoes preserved in amber. DNA from frogs, among other animals, was used to fill in gaps in the dinosaurs' genome. To prevent breeding, the dinosaurs were made female by direct chromosome manipulation. The group witnesses the hatching of a baby Velociraptor and visits the raptor enclosure. During lunch, the group debates the ethics of cloning and the park's creation. Malcolm warns of the implications of genetic engineering and scoffs at the park's design, saying it will inevitably break down.
Hammond's grandchildren, Lex and Tim, join the others for a tour of the park, while Hammond oversees them from the control room. Most of the dinosaurs fail to appear and the group encounters a sick Triceratops. The tour is cut short as a tropical storm approaches. The park employees leave for the mainland on a boat, while the visitors return to their railed-electric tour vehicles, except Sattler, who stays behind with the park's veterinarian, Dr. Harding, to study the sick Triceratops.
Jurassic Park's disgruntled lead computer programmer, Dennis Nedry, was previously bribed by Lewis Dodgson, a man working for Hammond's corporate rival, to steal frozen dinosaur embryos. He deactivates the park's security system to access the embryo storage room and stores them inside a container disguised as a Barbasol shaving cream can. Nedry's sabotage cuts power to the tour vehicles, stranding them as they near the park's Tyrannosaurus rex paddock. Most of the park's electric fences have also been deactivated, allowing the Tyrannosaurus to escape and attack the group. After the Tyrannosaurus overturns a tour vehicle, it injures Malcolm and devours Gennaro, while Grant, Lex, and Tim escape. On his way to deliver the embryos to the island's docks, Nedry gets lost in the rain, crashes his Jeep Wrangler, and is killed by a venom-spitting Dilophosaurus.
Sattler helps the game warden, Robert Muldoon, search for survivors; they find Malcolm just before the Tyrannosaurus returns and chases them away. Grant, Tim, and Lex take shelter in a treetop and encounter a Brachiosaurus herd. They discover the broken shells of dinosaur eggs the following morning. Grant concludes that the dinosaurs are breeding, which is possible because of amphibian DNA—animals like West African frogs can change their sex in a single-sex environment, enabling the dinosaurs to do so as well. The three later encounter a Gallimimus stampede being hunted by the Tyrannosaurus.
Unable to decipher Nedry's code to reactivate the security system, Hammond and chief engineer Ray Arnold decide to reboot the park's systems. The group shuts down the park's power grid and retreat to an emergency bunker, while Arnold heads to a maintenance shed to complete the rebooting process. When he fails to return, Sattler and Muldoon head over, discovering the shutdown has released the Velociraptors. Muldoon distracts two of them while Sattler turns the power back on before being attacked by a third and discovering Arnold's severed arm. Muldoon, simultaneously, is caught off-guard and killed.
Grant, Tim, and Lex reach the visitor center. Grant heads out to look for Sattler, leaving Tim and Lex inside. The raptors appear and pursue Tim and Lex throughout a kitchen, but they escape, locking one in a freezer before joining Grant and Sattler. The group reaches the control room, and Lex restores the park's systems, allowing them to contact Hammond, who calls for help. As they try to leave, they are cornered by the two remaining raptors, but the Tyrannosaurus appears and kills them while the group flees. Hammond arrives in a jeep with Malcolm, and they board a helicopter to leave the island.
